1. Field of the Invention
The invention pertains to a hopper loader apparatus for separating and forming an overlapping shingled stream of individual signatures of sheet materials from a vertically aligned, parallelepiped shaped stack of such signatures. The separated, individual signatures may then be subjected to subsequent handling operations.
2. Description of the Prior Art
In the graphic arts it is common that sheet materials such as newspapers, books, printed cartons and the like emerge from a printing operation in a serial stream of partially overlapping signatures in shingled form. Such a stream of signatures is typically collected on a conveyor and moved to a stacker for aligning. The stacker receives the sheets in a serial mode from the conveyor and forms a neatly aligned stack for removal and transportation. While large numbers signatures can be conveniently handled in stack form, some operations on the signatures can only be performed individually. It therefore becomes necessary to separate individual signatures from a stack for individual treatment. The present invention pertains to a vertical hopper loader for separating individual signatures, which are substantially vertically aligned on a folded edge, from a stack of signatures and then forming an overlapping shingled stream of individual signatures.
It has been a problem in the art to provide an efficient and effective means of separating a stack of signatures into its individual signatures for presentation to other equipment, such as a stitcher, a packer box on a binder line or the like. In the past, a stacked pile of printed signatures has been moved or pushed on a horizontal conveyor to an upwardly moving conveyor. Such an operation has many disadvantages since the stack does not reliably separate into evenly spaced overlapping individual signatures which inevitably leads to downstream signature jams and misfeeds requiring considerable operator attention. Complicated signature feeding equipment is known in the art. In this regard, U.S. Pat. No. 4,973,038 discloses a signature handling apparatus which uses a horizontal feed conveyor requiring a stack pusher. The signatures tend to slide down a second ramp conveyor and hence require a retainer wedge. U.S. Pat. No. 4,049,260 shows an apparatus for feeding sheets having a horizontal entry conveyor and a ramp conveyor with an abrupt transition to an exit conveyor. U.S. Pat. Nos. 5,282,613; 4,008,890 and 3,945,633 disclose other signature stream feeding apparatus.
The complicated nature of the construction and mode of operation of known on-edge signature supply assemblies leads to an irregular signature stream and increases the probability of a jam or other malfunction during operation of the signature supply assemblies. Slippage of on-edge signatures on conveyors is a significant problem with hopper loaders.
It has also been a problem in the art to reliably provide an efficient and effective means of separating a stack into its individual signatures and run reliably with a large range of signature sizes. The paper stock may range from heavyweight to lightweight and from a few pages to many pages per signature. This difference in paper weight and/or pagination has required the operator to perform many adjustments to make a machine ready for a production run. When multipage signatures having a bottom fold are moved on a folded edge, the forward motion of the conveyor, particularly a downwardly inclined conveyor tends to cause signatures to slide off conveyor chains. This results in paper jams, machine downtime and excess operator attention.
The present invention seeks to simplify hopper loader construction, reduce costs and avoid or reduce problems encountered in the prior art. Difficulties in operating vertical loaders arise in that a large quantity of signatures cannot be loaded in the loader without interfering with the feeding of signature at the supply station, and the loaders cannot handle very short and very long signatures without substantial changes in the feeding mechanism. Further, the signatures are subjected to a constant riffling, sliding and jostling action that results in damage to the folds on the signatures when they move between conveyor belts. The present invention provides a vertical loader which avoids or reduces problems encountered in the prior art. The invention provides an apparatus for separating individual signatures which are substantially vertically aligned on a folded edge from a stack of signatures and then feeding them to subsequent processing equipment.
According to the present invention a hopper loader which has a downwardly inclined entry conveyor is provided with a slippage resistant conveyor belt. Such a slippage resistant belt engages a bottom edge of an individual signature and assists in preventing the signature from slipping by not allowing the edge in contact with the belt to easily move away from its loading position on the belt. Preferably the slippage resistant belt has an array of projections extending upwardly from a belt surface which secures the signatures in place. This produces a smooth, regular, even signature stream. Individual signatures flow reliably, one-by-one off the downward conveyor to another conveyor.
According to one embodiment of the invention there is provided a hopper loader which has a downwardly inclined entry conveyor and an exit conveyor. The exit conveyor has an upwardly inclined planar ramp segment, an optional transition segment, and an exit segment. The transition segment has either a belt slide or a plurality of serially arranged rollers such that the arched transition segment has a radius of curvature sufficiently large such that a signature has a greater tendency to follow a path of the arched transition segment than to be propelled tangent to the upwardly inclined planar ramp segment.
In another embodiment of the invention, a hopper loader separates individual signatures which are substantially vertically aligned on a folded edge and moves them from a stack of signatures into a pocket from which they are fed by a feed mechanism to bindery equipment. The loader includes a downwardly inclined conveyor that moves a stack of signatures to an upwardly inclined conveyor which strips individual signatures from the stack and forms them into an overlapping shingled stream. The stream of signatures then moves to a product pocket including side walls, an indexing chain floor, and a stripper bar on the lower portion of each side wall. A product holdback deters selection of more than one signature at a time that is sent to the stitcher line. A vibrating jogger over the pocket used to even out the top of the product in the pocket one. Individual signatures flow reliably, one-by-one downwardly out of the pocket to bindery equipment. These and other features, advantages and improvements will be in part discussed and in part apparent to one skilled in the art upon a consideration of the detailed description of the preferred embodiment and the accompanying drawings.